Kawamoto Yasuhide, Morinaga Yoshitomo, Kimura Yumiko, Kaku Norihito, Kosai Kosuke, Uno Naoki, Hasegawa Hiroo, Yanagihara Katsunori
Department of Laboratory Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 851-2128, Japan.
Department of Laboratory Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 851-2128, Japan.
J Infect Chemother. 2017 Jan;23(1):51-55. doi: 10.1016/j.jiac.2016.09.010. Epub 2016 Nov 17.
TNF-α plays an important role in the pathogenesis of Legionella pneumophila (Lp)-induced pneumonia. Patients undergoing anti-TNF-α therapy are at an increased risk of Lp infection. Lp infects both phagocytic and non-phagocytic cells such as airway epithelial cells; however, the role of TNF-α in airway epithelial cells is unknown.
Human airway epithelial cell line NCI-H292 was infected with Lp NUL1 strain. After infection, both intracellular growth of Lp and cell death were evaluated after treating the cells with or without TNF-α. Apoptosis was examined by performing activated caspase-3/7 staining and by using a pan-caspase inhibitor.
Lp infected and replicated in NCI-H292 cells in a time-dependent manner, and TNF-α treatment of Lp-infected NCI-H292 cells inhibited Lp replication. Inhibitory effects of TNF-α on Lp replication were suppressed after treatment with a TNF-α-neutralizing antibody. Lp infection increased extracellular lactate dehydrogenase levels and decreased the number of living cells. Increased number of Lp-infected NCI-H292 cells showed caspase-3/7 activation, indicating they underwent apoptosis. TNF-α treatment inhibited Lp replication by increasing the apoptosis of NCI-H292 cells.
Thus, our results suggested that airway epithelial cells were involved in the pathogenesis of Lp infection and that TNF-α played a protective role by inhibiting the intracellular replication of Lp and by increasing the apoptosis of Lp-infected airway epithelial cells. However, Lp infection should be investigated further in patients undergoing anti-TNF-α therapy who develop pneumonia.
肿瘤坏死因子-α（TNF-α）在嗜肺军团菌（Lp）所致肺炎的发病机制中起重要作用。接受抗TNF-α治疗的患者感染Lp的风险增加。Lp可感染吞噬细胞和非吞噬细胞，如气道上皮细胞；然而，TNF-α在气道上皮细胞中的作用尚不清楚。
用人气道上皮细胞系NCI-H292感染Lp NUL1菌株。感染后，在用或不用TNF-α处理细胞后，评估Lp的细胞内生长和细胞死亡情况。通过进行活化的半胱天冬酶-3/7染色和使用泛半胱天冬酶抑制剂来检测细胞凋亡。
Lp以时间依赖性方式感染并在NCI-H292细胞中复制，用TNF-α处理Lp感染的NCI-H292细胞可抑制Lp复制。用TNF-α中和抗体处理后，TNF-α对Lp复制的抑制作用被抑制。Lp感染增加了细胞外乳酸脱氢酶水平并减少了活细胞数量。Lp感染的NCI-H292细胞数量增加显示半胱天冬酶-3/7活化，表明它们发生了凋亡。TNF-α处理通过增加NCI-H292细胞的凋亡来抑制Lp复制。
因此，我们的结果表明气道上皮细胞参与了Lp感染的发病机制，并且TNF-α通过抑制Lp的细胞内复制和增加Lp感染的气道上皮细胞的凋亡发挥了保护作用。然而，对于发生肺炎的接受抗TNF-α治疗的患者，应进一步研究Lp感染情况。
